Sleep-apnea syndrome is a medical condition characterized by daytime hypersomnolence, morning headaches, intellectual deterioration, cardiac arrhythmias, snoring and thrashing during sleep. It is caused by frequent episodes of apnea during the patient's sleep. The syndrome is classically subdivided into two types. One type, termed "central sleep apnea syndrome", is characterized by repeated loss of respiratory effort. The second type, termed "obstructive sleep apnea syndrome", is characterized by repeated apneic episodes during sleep resulting from obstruction of the patient's upper airway or that portion of the patient's respiratory tract which is cephalad to, and does not include, the larynx.
Treatment thus far includes various medical, surgical and physical measures. Medical measures include the use of medications such as protriptyline, medroxyprogesterone, acetazolamide, theophylline, nicotine and other medications in addition to avoidance of central nervous system depressants such as sedatives or alcohol. The medical measures above are sometimes helpful but are rarely completely effective. In addition, the medications frequently have distressing and sometimes dangerous side effects.
Surgical means have included uvulopalatopharyngoplasty, tonsillectomy, surgery to correct severe retrognathia and tracheostomy. These procedures may be effective but the risk of surgery in these patients can be prohibitive and the procedures are often unacceptable to these patients.
Physical measures have included weight loss, naso-pharyngeal airways, nasal CPAP and various tongue retaining devices used nocturnally. These measures may be partially effective but are cumbersome, uncomfortable and patients often will not continue to use these for prolonged periods of time. Weight loss may be effective but is rarely achieved by these patients.
In patients with central sleep apnea syndrome, phrenic nerve or diaphragmatic pacing has been used. Phrenic nerve or diaphragmatic pacing includes the use of electrical stimulation to regulate and control the patient's diaphragm which is innervated bilaterally by the phrenic nerves to assist or support ventilation. This pacing is disclosed in Direct Diaphragm Stimulation by J. Mugica et al. PACE Vol. 10 Jan-Feb. 1987, Part II, Preliminary Test of a Muscular Diaphragm Pacing System on Human Patients by J. Mugica et al. from Neurostimulation: An Overview 1985 pp. 263-279 and Electrical Activation of Respiration by Nochomovitez IEE Eng. in Medicine and Biology, June, 1983.
However, it was found that many of these patients also have some degree of obstructive sleep apnea which worsens when the inspiratory force is augmented by the pacer. The ventilation induced by the activation of the diaphragm also collapses the upper airway upon inspiration and draws the patient's tongue anteriorly down the throat choking the patient. These patients then require tracheostomies for adequate treatment.
A physiological laryngeal pacemaker as described in Physiological Laryngeal Pacemaker by F. Kaneko et al. from Trans Am Soc Artif Intern Organs 1985 senses volume displaced by the lungs and stimulates the appropriate nerve to open the patient's glottis to treat dyspnea. This apparatus would not be effective for treatment of sleep apnea. The apparatus produces a signal proportional to the displaced air volume of the lungs and thereby the signal produced is too late to be used as an indicator for the treatment of sleep apnea. There is often no displaced air volume in sleep apnea due to obstruction.
The only measure which is completely effective in obstructive sleep apnea is tracheostomy, however, this operation carries considerable morbidity and is aesthetically unacceptable to many patients.